This application claims the priority of German patent document 100 55 7572.1-22 filed Nov. 9, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process for real-time detection of obstacles for low-flying, airborne vehicles such as long distance communication wires and power cables. Such wires and cables constitute a potential hazard for aircraft operating at low altitudes, especially for helicopters.
A procedure for obstacle warning for low-flying aircraft is disclosed in DE 196 05 218 C1. There, range images of the scenery in front of the vehicle are generated by means of a sensor. The outlines (xe2x80x9ccontoursxe2x80x9d) of obstacles are extracted from the range images using high-pass filters to search for discontinuities occurring between adjacent pixels. Using a navigation system, the position of the obstacle contours can be graphically blended with the natural, forward-looking view of the external scenery. Actual detection of obstacles is not performed.
One object of the present invention is to provide a process for the detection of wires or cables, securely and in real time.
Another object of the inention is to provide such a detection process which requires a minimum of hardware.
These and other objects and advantages are achieved by the obstacle detection process according to the invention in which a front end range imaging sensor is used to scan the viewing field relative to the aircraft, while a navigation system provides information concerning the postion and attitude of the aircraft. A data processor uses these data to (generate 3-d scene vectors, such that every range image is converted into a measurement point set, from which the presence of cables or wires is detected using a wire detection procedure based on the Hough Transform. For this purpose, an HT acceleration board is provided, which needs not perform complex floating point operations. The processed results are then input to an evaluation module, which determines whether any detected wires are proximate to the position of the aircraft.
The procedure according to the invention has the following advantages:
maximum security in the process of wire detection by exploiting the three-dimensional geometry of the wire""s trajectory through space, including its slack;
possibility of precisely determining position and length of wire segments;
real-time performance with limited hardware; and
equal potential for day- and nighttime use.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.